1from __future__ import division
2from __future__ import unicode_literals
3#
4# Copyright 2005,2007,2012 Free Software Foundation, Inc.
5#
6# This file is part of GNU Radio
7#
8# GNU Radio is free software; you can redistribute it and/or modify
9# it under the terms of the GNU General Public License as published by
10# the Free Software Foundation; either version 3, or (at your option)
11# any later version.
12#
13# GNU Radio is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the GNU General Public License
19# along with GNU Radio; see the file COPYING.  If not, write to
20# the Free Software Foundation, Inc., 51 Franklin Street,
21# Boston, MA 02110-1301, USA.
22#
23
24import math
25from gnuradio import gr
26from gnuradio import blocks
27from gnuradio import filter
28
29class standard_squelch(gr.hier_block2):
30    def __init__(self, audio_rate):
31        gr.hier_block2.__init__(self, "standard_squelch",
32                                gr.io_signature(1, 1, gr.sizeof_float), # Input signature
33                                gr.io_signature(1, 1, gr.sizeof_float)) # Output signature
34
35        self.input_node = blocks.add_const_ff(0)          # FIXME kludge
36
37        self.low_iir = filter.iir_filter_ffd((0.0193,0,-0.0193),(1,1.9524,-0.9615))
38        self.low_square = blocks.multiply_ff()
39        self.low_smooth = filter.single_pole_iir_filter_ff(1 / (0.01*audio_rate))   # 100ms time constant
40
41        self.hi_iir = filter.iir_filter_ffd((0.0193,0,-0.0193),(1,1.3597,-0.9615))
42        self.hi_square = blocks.multiply_ff()
43        self.hi_smooth = filter.single_pole_iir_filter_ff(1 / (0.01*audio_rate))
44
45        self.sub = blocks.sub_ff();
46        self.add = blocks.add_ff();
47        self.gate = blocks.threshold_ff(0.3,0.43,0)
48        self.squelch_lpf = filter.single_pole_iir_filter_ff(1 / (0.01*audio_rate))
49
50        self.div = blocks.divide_ff()
51        self.squelch_mult = blocks.multiply_ff()
52
53        self.connect(self, self.input_node)
54        self.connect(self.input_node, (self.squelch_mult, 0))
55
56        self.connect(self.input_node,self.low_iir)
57        self.connect(self.low_iir,(self.low_square,0))
58        self.connect(self.low_iir,(self.low_square,1))
59        self.connect(self.low_square,self.low_smooth,(self.sub,0))
60        self.connect(self.low_smooth, (self.add,0))
61
62        self.connect(self.input_node,self.hi_iir)
63        self.connect(self.hi_iir,(self.hi_square,0))
64        self.connect(self.hi_iir,(self.hi_square,1))
65        self.connect(self.hi_square,self.hi_smooth,(self.sub,1))
66        self.connect(self.hi_smooth, (self.add,1))
67
68        self.connect(self.sub, (self.div, 0))
69        self.connect(self.add, (self.div, 1))
70        self.connect(self.div, self.gate, self.squelch_lpf, (self.squelch_mult,1))
71        self.connect(self.squelch_mult, self)
72
73    def set_threshold(self, threshold):
74        self.gate.set_hi(threshold)
75
76    def threshold(self):
77        return self.gate.hi()
78
79    def squelch_range(self):
80        return (0.0, 1.0, 1.0 / 100)
81